Surface profile detection for laser beam auto focusing

Auto-Focus Test Report
An Innovative Implementation of Transparent
S f fil i f h A li i fSurface Profile Detection for the Application of
Excimer Laser Beam Auto-Focusing
Dana Lee Church
TeoSys Engineering LLC
2138 Priest Bridge Ct Ste 102138 Priest Bridge Ct Ste 10
Crofton , MD 21114
443-713-8686 voice
410-989-6520 cell
Page 1 of 14TeoSys Engineering LLC Test Report, Rev. G 8/25/13
www.teosys.com

An Innovative Implementation of Transparent
Surface Profile Detection for the Application of
Excimer Laser Beam Auto-Focusingg
> Purpose, Abstract and Summary
Single page summery of full test
> Hardware Setup, Functionality and Installation
2
3Hardware Setup, Functionality and Installation
Description of the hardware setup, physical
installation in facility.
> Software and Data Collection
Applications functions and data collection process
3
5
> Static Testing (8 samples)
Testing of small samples of various glass using
the static flat fixture.
> Dynamic Testing – #1 Belt Conveyor
8
11
> Dynamic Testing – #2 Rubber Wheel Conveyor
> Results and Conclusions
12
14
Page 2 of 14TeoSys Engineering LLC

Purpose, Abstract and Summary
The purpose of Phase One was to demonstrate that an auto-focusing system could lock onto a moving glass surface
and maintain focus within +/ 100µm The system must use a non contact sensor The auto focus system was to beand maintain focus within +/- 100µm. The system must use a non-contact sensor. The auto-focus system was to be
made using existing, commercial off the shelf hardware.
A series of tests were conducted on August 19th thru 21st in
the Customer location in Belgium. The auto-focus system is
comprised of an optical module, an instrumentation cart and
several data acquisition PCs (ref Figure 1). This system
was initially installed on the #1 Belt Conveyor and
subsequently installed on the #2 Rubber Wheel Conveyor.
Control
Cart
Figure 1 : Test Setup on #2
The initial auto-focus testing involved evaluating whether
the system could recognize an assortment of possible glass
samples. In these tests the system successfully acquired
the first surface of the glass sample and successfully
focused on all eight samples presented. In nearly all cases
the system was also able to measure glass thickness
(within +/- 10µm), however thickness was not necessary for
the auto focus application Thickness measurement wasthe auto-focus application. Thickness measurement was
performed because it is an inherent capability of the sensor
system that was used.
Figure 2 is the auto-focus sensor display. In this live
screen capture of Sample #8 the system was able to
accurately focus on the first surface within 8µm and
measured the glass thickness as 6.244µm.
The dynamic tests conveyor moving tests were more
Optical Module
Glass Speed Encoder Wheel
Figure 2 : Sensor Display
challenging. On the #1 Belt Conveyor the system
successfully acquired and dynamically maintained focus
with a total error of less than +/- 50µm for all samples and
all speeds.
1st Surface
2nd
Surface
Focus Error and Thickness
For the #2 Rubber Wheel Conveyor the system initially maintained +/-
200µm focus. The #2 is a rougher conveyor with a rapid, bumpy profile.
After modifications were made to the control software the system
Figure 3 :
Successful Focus Run #2, Laminate Glass, 20mpm
Figure 3 displays a real-time sensor plot of the focusing
performance as measured on the most difficult glass
material (2 layer laminate) and on the most difficult conveyor
(#2). It is clear from this data that the auto-focus system is
After modifications were made to the control software, the system
successfully demonstrated +/- 100µm auto-focusing at 20 meters per
minute conveyor speed, using the most difficult laminated glass sample.
p( ) y
more than capable of maintaining focus within the +/-100 µm
range.
The focusing stage was damaged due to modifications made
to increase the speed above its rating, however sufficient
data was collected to successfully demonstrate the auto-
focus capability to address higher speeds on the #2
conveyor via faster hardware and programming.
The data in this report shows that the Phase One, auto-
focusing system was successfully able to demonstrate the
ability to acquire and track a glass surface on the worst case
presented conveyor within the given specification of +/-
100µm of error.
Glass Trailing Edge
Max Error
+100µm
- 100µm

Hardware Setup, Functionality and Installation Figure 4 : Demonstration
SystemThe Phase One demonstration system is comprised of
t j b t Th fi t b t i thtwo major sub-systems. The first sub-system is the
optical module. This device mounts above the
conveyor and contains the focusing stage, triangulation
sensor, emergency proximity sensor and associated
electronics. The second sub-system is the electronics
cart which contains the stage amplifiers, the main
control PC and a power supply system.
The electronics cart is not necessary for the final auto-The electronics cart is not necessary for the final auto
focusing system. It is used in this case for the testing
and evaluation of the focusing system as well as for
demonstrative purposes.
Displayed in Figure 4 are two additional laptops. The
center laptop monitors and displays the instantaneous
triangulation sensor data.
The right most laptop records and displays the focusing
(d lt Z f ) d th l thi kerror (delta Z focus error) and the glass thickness.
The demonstration system may be configured to
operate in three modes. The first mode is an
independent test which uses a flat fixture and a second
motion stage which moves a static glass sample up and
down in the vertical (Static Mode). This mode is used to
calibrate the sensor, tune the stages and test new glass
The second mode (Disc Mode) is a dynamic test used
to tune the responsivity of the auto focus system.
(Reference Figure 5).
Disc mode uses an acrylic disc to continuously
challenge the focusing system by providing both
calibrate the sensor, tune the stages and test new glass
materials.
horizontal motion as well as vertical movement.
Disc Mode is also used to calibrate an encoder wheel.
The encoder is used to record and correlate horizontal
motion with vertical displacement.
Figure 5 : Disc Mode

Hardware Setup, Functionality and Installation
The optical module with triangulation sensor was installed on two
Figure 7 : Adapter Plate
The optical module with triangulation sensor was installed on two
conveyors for testing (Figure 6). The first location was on the LG-#1
belt conveyor. This conveyor design is apparently the smoothest of
the conveyors presented with an vertical displacement profile of
approximately one millimeter.
The second location was on the #2 wheel conveyor, which depending
upon the wheel presented, had a vertical displacement profile of three
to four millimeters. In addition, the wheels contained small ‘bumps’ of
Rear Course
Vertical Adjustment
10mm in length or less. These bumps cause rapid vertical jumps in
the glass (500µm jumps up and down in less than 20ms!).
Figure 7 and Figure 8 both show details of the course vertical
adjustment, the adapter plate, the locking clamps and the bridge.
Fi 6
Second Location
Figure 6 :
Facility and Installation Locations
Locking
Clamps
Figure 8 :
Sensor Mounted on Bridge
First Location
omitted
omitted

Application Software and Data Collection
Figure 9 : Primary System Application Display
The primary system display on the
electronics cart is shown in Figure
9.
This application contains five
elements. The upper left display is
an analog live video of a set of
projected reticules which are
Figure 9 : Primary System Application Display
projected reticules which are
mounted to indicate focus error
values. The cross-hairs are focused
at zero error. The other numbers
come into focus as the glass surface
moves away from the desired zero
error focus plane.
The system has been designed to
d t t t 200 ’ fdemonstrate up to 200µm’s of error
in each direction.
NOTE: This display is completely
independent from the focusing
sensor and is intended to be an
independent validation that the data
collected is valid.
Auto focus Lock, -100µm Error Auto focus Lock, +100µm Error
collected is valid.
The display to the upper right in
Figure 6 monitors the motion
system feedback. The X axis is the
auto-focusing stage. The Z axis is
the speed feedback from the
encoder wheel and the U axis is not
used for this demonstration.
Figure 10 :
Analog display under various ‘out of focus’ conditions.
used for this demonstration.
The Y axis provides vertical
displacement which is used to
calibrate and test the system.
The graph on the lower right of
Figure 6 plots the motion of the X
and Y axes. In this example the Y
i i i t ti l l
Auto focus Lock, -200µm Error Auto focus Lock, +200µm Error
axis is moving a static glass sample
up and down (vertical displacement)
while the X axis automatically tracks
this motion. When successful auto-
focusing occurs, these two plots
should be nearly exact duplicates of
each other as is indicated in the
above example.
above example.
The other two displays in the lower
left of Figure 6 are used to
annotate video captures of the
screen and monitor critical system
variables.

Figure 11 : Focusing and Fixture Stage Motion Plot
X-Axis, Follower
(Focusing Stage)ns)
Figure 11 : Focusing and Fixture Stage Motion Plot
Y-Axis, Leader
(Stage, Simulates Glass Motion)
Position(micron
Time (Seconds)
Figure 13 :
Primary display under real world auto-focusing conditions.
Note that there is no Y axis motion, only X.
itt d
Page 7 of 14TeoSys Engineering LLC Test Report, Rev. F 8/25/10
omitted

The middle laptop runs an instantaneous triangulation sensor monitoring application. The triangulation sensor is
used to measure the distance from the objective lens to the glass work surface. This program displays the Auto
Focus Error (in mm), the glass plate thickness (in mm), as well as a two dimensional plot of the sensor response
as determined by the triangulation CCD. Each peak represents a surface detected and the position along the X
axis represents the distance from the sensor to the glass surface. When the sensor ‘locks’ onto a surface it
imposes a vertical line on the display.
The triangulation sensor is
mounted on the stage and is
Figure 14 : Current Sensor Monitor Display
g
being used in ‘Differential
Mode’. This means that the
sensor actually measures the
distance (+/-) from the ideal
focus plane. As the glass plate
moves up and down (vertical
displacement) the sensor
detects the differential errordetects the differential error
between the desired focal
location and the current focal
location. There are many
tradeoffs with the
implementation of differential
mode, however the primary
benefit of this approach is that itpp
requires no math or special
electronics to integrate the
sensor signal into the motion
control focusing module.
The final laptop (Figure 15) is a
custom data logger application
which tracks the short and long
Figure 15 : Data Logger Application Display
which tracks the short and long
term focus error. This display
is calibrated and annotated to
provide a quick and easy way
to evaluate the results from all
tests. The horizontal axis is
time and the vertical axis is
displayed in microns. Eachp y
axis is dynamically scalable.
The triangulation sensor is configured to collect data every 100us. The data logger collects a data point from the
triangulation sensor every 4ms and displays it on a graph. The digital display to the upper right is the
instantaneous focusing error which is calibrated to microns whereas the graph on the left is a long term record of
the data. The image in Figure Fifteen displays a typical panel in motion without auto focus running. It displays
the vertical displacement profile of a glass panel moving along a conveyor.
NOTE: The data of the long term plot (on the left) is mirrored in the center. The conveyor operator reversed the
plate in the middle of motion and this its vertical displacement was captured by the sensor and displayed in the
data logger. The nearly exact mirror of the data provides confidence that the sensor is reading the actual
physical surface attributes and not just reflecting noise.

Static Testing ( 8 Sample Test )
The static glass sample testing verified that each sample would ‘lock’ with the sensor and could close the auto-g p g p
focus loop. Each sample was photographed and a screen capture of the sensor monitor taken. Not all screen
captures were taken with the auto focus system enabled so the absolute error figure is not significant.
Sample 1– Dark Blue
omitted
Sample 2 – Grey
Good Lock on First Surface (Focus)
Good Thickness Measurement of 5.911mm
omitted
Sample 3 – Taupe
omitted

Sample 4 – Black Opaque
omitted
Lock – Signal Saturated
No Thickness Measurement
Sample 5 – Coated for Solar - Green
omitted
Good Thickness Measurement
Sample 6 – Acid Etched, Clear
omitted
No Thickness on Acid Etched Sample

Sample 7 –Clear Float
omitted
No Thickness
omitted
Sample 8 – Additional Clear Float
omitted
Good Thickness of 6.244mm
In all cases these measurements were taken without adjustment to the sensor parameter algorithm or alteration
to the sensor optical path. With addition of optical filters, adjustments to sensor angle, and changes to sensor
acquisition algorithm it is highly probable that all sensor responses can be optimized to be acquired reliably. With
th dditi f d h d t thi k l th b bilit f d thi k l kthe addition of a second sensor head to measure thickness only, the probability of a good thickness lock
increases by an order of magnitude. NOTE: Thickness measurements are not a requirement for auto-focusing.
In each stationary test, the auto focus system was able to reliably acquire the sample top surface. With the
current system configuration, which isn’t fully optimized, the auto focus system reliably demonstrates that it can
acquire and lock on the first surface to within +/- 10µm on all stationary tests. The error value measurement, as it
comes from the triangulation sensor, appears to accurate within +/- 5µm
Page 11 of 14TeoSys Engineering LLC Test Report, Rev. F 8/25/10
The Phase One stationary testing demonstrated that for all presented glass materials, the sensor reliably and
successfully acquired and locked on the glass top surface. This was done without optimization or adjustment
between tests.

Dynamic Testing, #1 - Belt Conveyor
The Belt Conveyor proved to be quite smooth and easiest conveyor on which to auto-focus. Below are real time
screen captures of all of the tests at the various speeds taken on the #1 Belt. Without the auto focus enabled, the
vertical displacement profile that was measured with the glass on the #1 conveyor, is less than one millimeter. The
key difference with the Belt Conveyer versus the Wheel Conveyor is that its oscillations are slower and shallower.
With auto focus enabled, the maximum focusing error was much less than 50 microns on the #1.
Max Error +/- 20µmMax Error +/- 10µm Max Error +/- 20µm
Speed 16 mpm
Max Error +/ 10µm
Speed 1 mpm
Max Error +/- 15µm
100% In Focus100% In Focus
Max Error +/- 20µm
Speed 20 mpm Speed 30 mpm
100% In Focus100% In Focus
Max Error + 8, - 30 µm
Speed 40 mpm
Max Error + 8, - 35 µm
Speed 50 mpmSpeed 40 mpm Speed 50 mpm
100% In Focus 100% In Focus

Dynamic Testing, #2 – Rubber Wheel Conveyor
The rubber Wheel Conveyor was more difficult of a conveyor on which to auto focus Below are real time screenThe rubber Wheel Conveyor was more difficult of a conveyor on which to auto-focus. Below are real time screen
captures of several of the tests at various speeds taken on the #2 Conveyor. The bumps on the wheels are often
10mm or less in length creating short quick spikes, which are the most difficult types of oscillations to track.
Without the auto-focus enabled, the vertical displacement profile that was measured with the presented material
was several millimeters depending upon the randomness of which wheels are being presented to the glass plate.
Speed 1 mpm
Depicted in the display to the right
is the vertical displacement profile
of a glass sample with auto-focus
enabled and then auto-focus
disabled.
At 1 mpm with auto-focus enabled
Max Error
+ 150µm / - 25 µm
Auto Focus ON OFF
Max Error
+ 550µm / -100 µm
At 1 mpm, with auto focus enabled,
the total error is less than 175µm.
At the half way point where the auto
focus is turned off, the total error
jumps to 650µm.
When run at speed it became clear that the auto-focus system motion hardware (lead-screw stage) was not
fast enough to maintain focus within the +/- 100µm requirement. At 16 mpm the auto-focus error is just within
the +/- 100µm requirement. At 20 mpm the error exceeds the specification. With increasing conveyor speeds
the auto-focus error also increases.
Max Error +/- 100µm
Speed 16 mpm
Speed 20 mpm
Max Error +200µm
-125µm
In Focus Not In Focus

Dynamic Testing, #2, Rubber Wheel Conveyor
T dd th d li it ti f th ti h d (l d t ) dj t t d t thTo address the speed limitation of the motion hardware (lead-screw stage), adjustments were made to the
application programming and focus stage speeds. The focusing stage used for this demonstration is comprised
of an older lead screw design. This stage is not the optimum component for this application but was used for the
demonstration in order to meet the schedule constraints. In the actual production system, a linear stage would
be used. Linear stages are lighter, faster and more rugged.
System responsivity was increased in order to meet the demands of the Wheel Conveyor by eliminating the
system safety features, by reducing the software overhead and by increasing the stage velocity by almost ay y , y g y g g y y
magnitude faster than its recommended safe speed.
Speed 20 mpm
These adjustments were extremely successful in the
reduction of focus error.
The plot on the right shows an initial early adjustment
(speed from 350 to 550). At this higher stage speed
it is apparent that the responsivity of the auto-focus
has improved and that the error has been reduced.
Max Error
+100µm
- 200µm
has improved and that the error has been reduced.
Speed 20 mpmIn Focus
Increasing the focus stage speed to 650 brings us
within specification compliance. At this higher stage
speed the responsivity has improved again and all
tracking is within +/- 100µm.
Increasing the speed to 950 improved the total
system performance at 20mpm and all tests reside
Max Error
+100µm
- 100µm
system performance at 20mpm and all tests reside
within +/-100µm.
Without the stage safety constraints in place, the
auto-focus stage was subject to certain limitations.
Unfortunately, the stage was run too fast and
exceeded its allowable current profile and it stopped
performing. With the system safety checks in place,
Speed 20 mpmIn Focus
p g y y p ,
this is not a problem but with the protections turned
off and the stage driven beyond its maximum speed.
Given the data collected, it is apparent that with the
appropriate hardware and software, the auto-focus
system is able to cut the tracking error in half and
increase glass speed to 30 or 40 mpm on the worst
case #2 Wheel Conveyor
Max Error
+100µm
- 100µm
case #2 Wheel Conveyor
The data collected in these speed tests, clearly and repeatably demonstrates +/- 100µm tracking, at nominal
operating speeds, on the most difficult conveyor system presented.

Results and Conclusions
For this testing the auto-focus demonstration system was able to exhibit the following;For this testing, the auto-focus demonstration system was able to exhibit the following;
1. 100% accurate acquisition of glass first surface using non-contact sensor.
2. Thickness measurement for most glass samples, although not necessary for auto-focusing operation.
3. Demonstrated focusing error measurement to within +/- 5µm on static testing.
4. Demonstrated focusing error acquisition at a 10 KHz acquisition rate from sensor.
5 Demonstrated thickness measurement to +/ 15µm although not necessary for auto focusing operation5. Demonstrated thickness measurement to +/- 15µm, although not necessary for auto-focusing operation.
6. Demonstrated numerous safety features including advanced fiber proximity detector which rapidly
retracts focusing head when an interference is detected.
7. Demonstrated independent video acquisition system which validates focus lock in real time via the use
of an innovative three dimensional reticle projection system.
8. Demonstrated advanced custom TeoSys data logging and display application which allowed complete
capture of all events and facilitated post testing analysiscapture of all events and facilitated post testing analysis.
9. Demonstrated full auto-focus lock within specification (+/-100µm) for eight production glass samples.
10. Demonstrated full static and dynamic auto-focus lock within specification for multi-layered laminates.
11. Demonstrated full dynamic in-focus performance within specification, on the #1 conveyor for all speeds,
1 to 50 meters per minute.
12. Demonstrated full dynamic in-focus performance within specification, on the #2 conveyor for speeds upy p p y p p
to 20 meters per minute.
The testing of TeoSys’s auto-focus system was successful and exceeded all of our goals for the initial Phase
One demonstration. Constructed with available off-the-shelf hardware as well as custom parts and software,
the TeoSys auto-focus system was able to maintain focus 100% of the time on all glass samples and all
speeds presented on the #1 conveyor. There were no issues whatsoever with this testing.
While the #2 conveyor was more challenging, the auto-focus was able to maintain focus 100% of the time on
all glass types up to speeds of 20 meters per minute. Over 20 meters per minute, the limiting factor was the
mechanical stage speed of the off-the-shelf focusing stage that was used for this demonstration.
Epilog:
After all other testing was complete and to prove to ourselves that the mechanical speed of the focusing
stage was in fact the limiting factor, we pushed the stage well beyond its recommended operational speed.
In this testing we significantly improved the ability to maintain focus at speeds over 20 meters per minute on
the #2 conveyor and thus confirmed that the focusing stage was the limiting factor. As a result of the data
collected, TeoSys is absolutely confident in our ability to maintain focus on all conveyors with line speeds
above 20 meters per minute and on all transparent non etched glass samples
above 20 meters per minute and on all transparent, non-etched glass samples.

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